The present invention is directed to a tool for dispensing a single component or multi-component mass located within a cartridge or foil bag by pressing the mass out of the cartridge or foil bag. The tool includes at least one advancing or feeding mechanism for at least one piston rod. The advancing mechanism comprises at least two clamping levers which can be pivoted in the axial direction of the piston rod and can also be axially displaced along the rod. In addition, at least two springs cooperate with the clamping lever along with one triggering lever and an unlocking lever. A first one of the clamping levers serves to advance the piston rod while the second one of the clamping levers locks or latches the piston rod, and the unlocking lever cooperates with the second one of the clamping levers as well as with the piston rod.
A single component or a multi-component mass is used at the present time for many varied applications in buildings, motor vehicles, ships, aircraft, machines, instruments and many other apparatuses. To afford convenient handling for the tool operator, the mass is usually supplied in small containers such as cartridges or foil bags, which can be inserted into the tool and pressed or squeezed out.
A manually operated dispensing tool for multi-component masses is disclosed in CH-PS 663 733. To prevent a return stroke of the piston rod when the first clamping lever regrips the rod for the advancing step, the tool includes a second clamping lever for each piston rod which serves to lock the piston rod in place. Such a second clamping lever must be released so that the piston rods can be pulled back to their original position. This return action is effected by an unlocking lever in engagement with the second clamping lever.
In this known dispensing tool, the arrangement of the advancing and unlocking mechanism has proved to be disadvantageous. The first clamping lever serving for advancing the piston rod is located in a central entrainment element disposed in such a way on the piston rod that in its initial position it rests at a stop face extending at a right angle to the axial direction of the piston rod. When the triggering lever is actuated, the first clamping lever is pivoted relative to the piston rod providing a clamping action by the clamping lever on the shaft piston rod. Only when the triggering lever is further actuated does the advancing of the piston rod take place. In such an advancing mechanism a part of the actuation travel of the triggering lever is always used for clamping the clamping lever against the piston rod. This has a disadvantageous effect on the handling of the dispensing tool and also on the processing time for the masses disposed in the cartridges in the tool.
If unhardened piston rods are used, wear can take place in the shaft region of the rod. Such wear is noticeable as a reduction in the diameter of the piston rod. To reach a clamping position of the first clamping lever acting to advance of the piston rod where the rod is worn, additional actuation travel of the triggering lever is necessary and, as a result, there is less actuation travel for the actual advancing of the piston rod.
Another disadvantage is experienced with the unlocking mechanism, where the unlocking lever acts upon the second clamping lever which serves to lock the piston rod. When the piston rod has reached the end of the dispensing operation when the mass has been completely squeezed out, in this front end position actuation elements disposed on the piston rod act on the unlocking lever. Accordingly, the piston rod is not locked in its front end position. A force transmitted by the triggering lever to the first clamping lever acts fully on the front region of the tool in the dispensing direction. As a result, damage can occur in that region and could finally lead to destruction of the tool.